1. Field of the Invention
The present invention relates to an optoelectronic sensor which is capable of measuring rotational and/or linear motion, as well as the rate of flow of a fluid.
2. Description of the Related Art
Rotation or yaw rate sensors are desirable for advanced mechanical control systems such as active-suspension and anti-skid braking systems for automotive vehicles. Known rotation sensors such as mechanical gyroscopes, ring lasers, fiber-optic ring interferometers, and variations of liquid-suspended floating rotors are far too expensive for automotive applications.
Another type of sensor manufactured by Applied Technology Associates, Inc., of Albuquerque, NM senses the fluid motion of liquid mercury in a magnetic field. The sensor is described in a data sheet distributed by said manufacturer entitled "A VERSATILE WIDE DYNAMIC RANGE MHD ANGULAR SENSOR", by M. Hawes et al. Shearing motions of the conducting mercury relative to the magnetic field result in a magnetohydrodynamic (MHD) voltage.
The principal disadvantage of the MHD sensor is that the signal voltages are very small, typically on the order of one microvolt, for rotations of interest to automotive applications. Low signal levels and resulting poor signal to noise ratios require expensive low noise amplifiers and signal conditioning circuitry, which preclude the application of MHD sensors to automotive systems which require low cost components.